1. Field of the Invention
The present invention relates to a surface mountable crystal oscillator, such as a quartz oscillator, which is press-inserted into a cylindrical case in vacuum or an inert gas atmosphere and is airtightly sealed and, more specifically, to a crystal oscillating device having a crystal oscillator and to a method of producing the crystal oscillating device.
2. Background Information
In recent years, a portable, small and lightweight information terminal such as a pager, a portable telephone, and a PHS have become popular. In order to increase the mounting density to a circuit board an electric part which can be mounted on the surface of the circuit board by reflow soldering or the like, is used. A quartz oscillator as a reference of a time or a frequency is mounted in such electric instruments. Concerning the quartz oscillator as well, various surface mounting types have been proposed and have been put into practical use for miniaturization, lightening, thinning, or automatization of assembly.
Japanese Patent Application Laid-Open No. Hei. 4-77103 discloses a cylindrical quartz oscillator airtightly sealed in an outer case having an opening portion. The cylindrical quartz oscillator is brought into close contact with the outer case having a storage space and is stored therein. A lead terminal of the cylindrical quartz oscillator is bent toward an outside bottom surface of the outer case. Two dummy terminals are provided at the outside bottom surface of the same outer case. The dummy terminals can be soldered to a board.
However, such a conventional quartz oscillator has problems as follows. When the case storing the quartz oscillator is used, if the case has a complicated shape, the cost is high and the assembly is not easy. Since the quartz oscillator is stored in the outer case while being brought into close contact with the storage space of the outer case, the quartz oscillator may slide relative to the storage case, or get out of place. Further, since the outer lead terminal is bent toward the bottom surface of the case, the outer lead terminal is concealed by the case, so that positioning accuracy at mounting to a printed wiring board and the inspection of connection and fixation becomes extremely difficult, and there is a fear that the quartz oscillator falls out of the board by a shock. Moreover, there is a fear that only with a flexible or metal cover, heating at reflow may have a bad influence on the characteristics of the quartz oscillator.
Thus by the foregoing conventional surface mounting quartz oscillator, it has been extremely difficult to realize a quartz oscillator having high accuracy, which can be easily assembled with the fewest possible parts.